One of methods for applying copper plating or bronze plating to iron and steel is immersion plating involving immersion of a member to be plated in a plating solution containing copper sulfate or containing copper sulfate and stannous sulfate. This immersion plating utilizes a difference in ionization tendency between iron and copper or tin, and iron is dissolved, in an amount depending on the amount of the plating copper or bronze, in a waste plating solution.
Since the waste plating solution contains cations such as Cu ions and Fe ions and anions such as sulfate ions, it was neutralized and then an aggregating agent was added thereto to aggregate the cations for recovery of the metals so that a clean waste solution was drained.
As a method for recovering metals from a waste plating solution, there is disclosed a method comprising passing a waste tin plating solution containing Fe ions and Sn ions through a strongly acidic cation-exchange resin to adsorb and recover cations onto the cation-exchange resin, and then passing an acid solution through the cation-exchange resin on which the cations are adsorbed to recover the cations in the acid, thereby precipitating and separating Sn (Patent Document 1).